Swash plate type variable displacement compressor

ABSTRACT

A swash plate type variable displacement compressor includes a housing, a drive shaft, a piston, a lug plate, a swash plate, a hinge mechanism provided between the lug plate and the swash plate, and a control mechanism. The hinge mechanism includes a restraining hinge element that is located on a suction side with respect to a first imaginary plane that includes a top position of the swash plate corresponding to the top dead center position of the piston and the axis of the drive shaft for restraining the lug plate and the swash plate from rotating relative to each other and the swash plate to move away from the lug plate. The hinge mechanism further includes a non-restraining hinge element that is located on a discharge side with respect to the first imaginary plane for not restraining the swash plate from moving away from the lug plate.

BACKGROUND OF THE INVENTION

The present invention relates to a swash plate type variable displacement compressor.

Japanese Patent Application Publication No. 9-203377 discloses a conventional swash plate type variable displacement compressor (hereinafter referred to merely as “compressor”). The compressor includes a housing that defines therein a cylinder bore, a crank chamber, a suction chamber and a discharge chamber, a piston that is reciprocatably accommodated in the cylinder bore for defining a compression chamber and a drive shaft that is driven by an external drive source and rotatably supported by the housing. The compressor further includes a lug plate that is supported in the crank chamber so as to rotate integrally with the drive shaft and a swash plate that is supported in the housing so as to rotate integrally with and incline relative to the drive shaft through the lug plate and a hinge mechanism for reciprocating the piston through shoes. The swash plate has an elongated hole which is formed at the center thereof with parallel facing surfaces and through which the drive shaft is inserted for receiving the outer circumferential surface of the drive shaft. Furthermore, the compressor includes a control mechanism for controlling the pressure in the crank chamber.

The hinge mechanism of the compressor includes an arm and an engaging groove as a non-restraining hinge element, which is located adjacent to the top position of the swash plate corresponding to the top dead center position of the piston and on an imaginary plane including the top position and the axis of the drive shaft and does not restrain the swash plate from moving away from the lug plate. The arm is provided on the swash plate and has a first guide surface that faces toward the lug plate. The engaging groove is formed in the lug plate and has a second guide surface that is contactable with the first guide surface. In the non-restraining hinge element, the top end of the arm is held in the engaging groove, thereby restraining the lug plate and the swash plate from rotating relative to each other.

The compressor constructed as described above constitutes together with a condenser, an expansion valve and an evaporator a refrigerant circuit for use in a vehicle. As the drive shaft is driven by an engine or the like as the external drive source and the swash plate is rotated at an inclined angle, the piston is reciprocated in the cylinder bore. Thus, a refrigerant gas is drawn from the suction chamber into the compression chamber in the cylinder bore, compressed and then discharged into the discharge chamber. The control mechanism adjusts the pressure in the crank chamber so as to vary the inclination angle of the swash plate, thereby controlling the amount of the refrigerant gas discharged from the compression chamber into the discharge chamber. Thus, cooling performance in accordance with the discharged amount of the refrigerant gas is achieved by the refrigerant circuit.

During operation of the compressor, a compression reactive force and a suction force of the refrigerant gas are applied to the swash plate through the piston and the shoes thereby to create a moment thereon which urges the swash plate to turn around the intersection line between the swash plate and the above imaginary plane to be inclined relative to the drive shaft. In the non-restraining hinge element in which the top end of the arm is held in the engaging groove, both side surfaces of the arm are brought into contact with the inner side wall surfaces of the engaging groove, respectively, thereby to receive the moment. The elongated hole formed at the center of the swash plate receives the moment at the parallel facing surfaces thereof.

Japanese Patent Publication No. 2917767 discloses a compressor having a hinge mechanism that is different from the above-described hinge mechanism. In this compressor, the hinge mechanism includes a pair of restraining hinge elements that are located on the suction side and the discharge side, respectively, with respect to the above imaginary plane for restraining the lug plate and the swash plate from rotating relative to each other and the swash plate from moving away from the lug plate, in place of the above-described arm and the engaging groove as the non-restraining hinge element. Each of the restraining hinge elements includes a support arm that is provided on the lug plate and has a guide hole, and a guide pin that is provided on the swash plate and has a spherical portion for sliding in the guide hole.

In the above-described compressor of Japanese Patent Publication No. 2917767, the pressure in the crank chamber is adjusted by the control mechanism to vary the inclination angle of the swash plate, thereby controlling the amount of refrigerant gas discharged from the compression chamber into the discharge chamber, as in the compressor of Japanese Patent Application Publication No. 9-203377.

During operation of the compressor, the pair of restraining hinge elements receive the moment that urges the swash plate to turn around the intersection line between the swash plate and the above imaginary plane to be inclined relative to the drive shaft. Also, the elongated hole formed at the center of the swash plate also receives the moment at the parallel facing surfaces.

However, problems arise in the above compressors in the reduction of vibration and noise during operation of the compressor as described below.

In the compressor of Japanese Patent Application Publication No. 9-203377, when the compressor operates at a high speed and under a large displacement in a state where the refrigerant is insufficient in the refrigerant circuit, the piston reciprocates for a large stroke length at high speed, but the discharge pressure is not increased to a desired value due to the insufficient refrigerant gas. Thus, the inertial force of the piston tends to become greater than the compression reactive force, thereby creating a moment acting on the swash plate to urge the inclination angle of the swash plate to be increased. The hinge mechanism of Japanese Patent Application Publication No. 9-203377 having the non-restraining hinge element with no function of restraining the swash plate from moving away from the lug plate does not receive the above moment created by the excessive inertial force of the piston and urging the swash plate to be inclined further. Thus, there is a fear that the swash plate may be inclined beyond its maximum inclination angle. In this case, the piston reciprocates for a distance longer than the maximum stroke and the piston head collides against the suction valve at the top wall of the compression chamber, with the result that abnormal noise and vibration are generated.

In the compressor of Japanese Patent Publication No. 2917767, since the hinge mechanism has the pair of restraining hinge elements that restrain the swash plate from moving away from the lug plate, the hinge mechanism receives the moment created by the above excessive inertial force of the piston and urging the swash plate to be inclined further. Therefore, the swash plate is not inclined beyond its maximum inclination angle and, therefore, generation of abnormal noise and vibration due to the excessive inclination of the swash plate beyond the maximum inclination angle is prevented.

However, in the compressor of Japanese Patent Publication No. 2917767, each of the restraining hinge elements restrains the lug plate and the swash plate from rotating relative to each other and the swash plate from moving away from the lug plate and, for ensuring smooth movement of the hinge mechanism, the clearance of each restraining hinge element needs to be enlarged appropriately. This is because reducing the clearance of the restraining hinge element while simultaneously ensuring the accuracy of positioning of the restraining hinge elements is difficult in view of production cost and productivity of compressors which are usually mass-produced. Large clearance of the restraining hinge elements may cause a play between the swash plate and the shoes and also between the shoes and the piston. When the compressor is operating under its minimum displacement, the compression reactive force and the suction force acting on the swash plate become minimum and, therefore, abnormal and hence unpleasant noise and vibration may be generated in the compressor around the swash plate, shoes and a piston. Such a compressor which is mounted in a vehicle may discomfort a vehicle occupant therein.

The present invention is directed to a swash plate type variable displacement compressor that reduces the generation of noise and vibration in operation.

SUMMARY OF THE INVENTION

According to the present invention, a swash plate type variable displacement compressor for compressing a refrigerant includes a housing, a drive shaft, a piston, a lug plate, a swash plate, a hinge mechanism and a control mechanism. The housing defines therein a cylinder bore, a crank chamber, a suction chamber and a discharge chamber. The piston is reciprocatably accommodated in the cylinder bore and defines a compression chamber in the cylinder bore. The drive shaft is driven by an external drive source and rotatably supported by the housing. The lug plate is supported by the drive shaft in the crank chamber so as to rotate with the drive shaft. The swash plate is supported by the drive shaft in the crank chamber. The hinge mechanism is provided between the lug plate and the swash plate. The swash plate is rotatable with and inclinable relative to the drive shaft through the lug plate and the hinge mechanism for reciprocating the piston through shoes. The control mechanism is operable to control a pressure in the crank chamber thereby to vary an amount of the refrigerant discharged from the compression chamber into the discharge chamber by the reciprocation of the piston based on an inclination angle of the swash plate. The hinge mechanism includes a restraining hinge element that is located on a suction side with respect to a first imaginary plane that includes a top position of the swash plate corresponding to a top dead center position of the piston and an axis of the drive shaft for restraining the lug plate and the swash plate from rotating relative to each other and the swash plate to move away from the lug plate. The hinge mechanism further includes a non-restraining hinge element that is located on a discharge side with respect to the first imaginary plane for not restraining the swash plate from moving away from the lug plate.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a longitudinal cross-sectional view of a swash plate type variable displacement compressor according to a preferred embodiment of the present invention;

FIG. 2 is a partially enlarged cross-sectional view of the compressor according to the preferred embodiment of the present invention as seen from the back side of FIG. 1;

FIG. 3 is a top view of a swash plate according to the preferred embodiment of the present invention;

FIG. 4 is a front view of the swash plate according to the preferred embodiment of the present invention;

FIG. 5 is a partially enlarged cross-sectional view of the compressor according to the preferred embodiment of the present invention showing the inclination of the swash plate at a minimum inclination angle;

FIG. 6 is a partially enlarged cross-sectional view of the compressor according to the preferred embodiment of the present invention as seen from the back side of FIG. 5 and showing the inclination of the swash plate at a minimum inclination angle; and

FIG. 7 is a schematic top view of the swash plate, the hinge mechanism and a lug late according to the preferred embodiment of the present invention showing the relationship between the lug plate and the swash plate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following will describe a preferred embodiment according to the present invention with reference to FIGS. 1 through 7. Referring to FIG. 1, the swash plate type variable displacement compressor 10 of the preferred embodiment (hereinafter referred to as “compressor”) has a housing 1, single-headed pistons 31, a drive shaft 16, a lug plate 24, a swash plate 25 and a control mechanism 4. In FIG. 1, the left side and the right side correspond to the front side and rear side of the compressor 10, respectively.

The housing 1 includes a cylinder block 11, a front housing 12 joined to the front end of the cylinder block 11 and a rear housing 13 joined to the rear end of the cylinder block 11 through a valve plate 14. The front housing 12 and the rear housing 13 are fixed to the cylinder block 11 by bolts (not shown). The cylinder block 11 and the front housing 12 cooperate to define therein a crank chamber 15.

The drive shaft 16 is rotatably supported by the cylinder block 11 and the front housing 12. More specifically, a coil spring 17 and a thrust bearing 18 are disposed in a shaft hole 80 formed in the cylinder block 11 at the center thereof, and the drive shaft 16 is supported at the rear end thereof by the thrust bearing 18 that is urged forward by the coil spring 17. The drive shaft 16 is supported also at a position adjacent to the front end thereof by a radial bearing 19 that is disposed in a shaft hole 81 formed in the front housing 12. A seal device 20 is provided in the shaft hole 81 in front of the radial bearing 19. Furthermore, the drive shaft 16 is connected at the front end thereof to a pulley 21 which is provided on the front end of the front housing 12 through a bearing 90. The pulley 21 is rotatable with the drive shaft 16. The pulley 21 is connected through a belt 91 to a vehicle engine as an external drive source. Thus, the compressor 10 is constantly driven by the engine during operation of the engine.

The lug plate 24 is press fitted on the drive shaft 16 in the crank chamber 15. A thrust bearing 27 is provided between the lug plate 24 and the inner wall surface of the front housing 12. The swash plate 25 is mounted on the drive shaft 16 and has an elongated hole 22 through which the drive shaft 16 is inserted. The elongated hole 22 is formed at the center of the swash plate 25 and has parallel facing surfaces 23 for receiving the outer circumferential surface of the drive shaft 16 as shown in FIGS. 3 and 4. A hinge mechanism 26 is provided between the lug plate 24 and the swash plate 25.

Referring to FIG. 1, a spring 28 is provided on the drive shaft 16 between the lug plate 24 and the swash plate 25. The spring 28 serves to urge the swash plate 25 toward the cylinder block 11, that is, in the direction that causes the inclination angle of the swash plate 25 to be decreased. A circlip 29 is fixed on the drive shaft 16 behind the swash plate 25. A spring 30 is provided on the drive shaft 16 between the circlip 29 and the swash plate 25. When pressed by the swash plate 25, the spring 30 serves to urge the swash plate 25 away from the cylinder block 11, that is, in the direction that causes the inclination angle of the swash plate 25 to be increased.

The cylinder block 11 defines therein a plurality of cylinder bores 11 a that are equiangularly arranged around the drive shaft 16. Only one cylinder bore 11 a is shown in the drawings. Each of the cylinder bores 11 a extends parallel to the drive shaft 16, and the piston 31 is reciprocatably disposed therein. Each of the pistons 31 is engaged at the front end thereof with the outer periphery of the swash plate 25 through a pair of shoes 32. Each shoe 32 has a substantially semispherical surface in contact with the piston 31 and a flat surface in contact with the swash plate 25. The paired shoes 32 are disposed on the opposite sides of the swash plate 25 so that they form a substantial spherical shape.

A compression chamber 33 is defined in each cylinder bore 11 a between the piston head of the pistons 31 on the rear side and the valve plate 14. When the swash plate 25 is rotated with the drive shaft 16 while being inclined relative to the drive shaft 16, a wobbling motion of the swash plate 25 is generated thereby to reciprocate each of the pistons 31 through the associated paired shoes 32. In this manner, the rotation of the drive shaft 16 is converted into the reciprocating movement of the pistons 31 through the swash plate 25 and the shoes 32.

The rear housing 13 defines therein a discharge chamber 34 and an annular suction chamber 35 surrounding the discharge chamber 34. The suction chamber 35 is connected to a refrigerant circuit 37 on the downstream side through an inlet 36 formed in the rear housing 13. The discharge chamber 34 is connected to the refrigerant circuit 37 on the upstream side through an outlet 38 formed in the rear housing 13. The refrigerant circuit 37 includes a condenser 39, an expansion valve 40 and an evaporator 41.

The valve plate 14 has a suction port 42 and a discharge port 43 that are correspondingly disposed in relation to each compression chamber 33. The valve plate 14 also has a suction valve 42 a and a discharge valve 43 a that are correspondingly disposed in relation to each suction port 42 and each discharge port 43, respectively. During the suction stroke of the piston 31, a refrigerant gas in the suction chamber 35 is drawn into the compression chamber 33 through its associated suction port 42 while pushing open the suction valve 42 a. During the compression stroke of the piston 31, on the other hand, the refrigerant gas is compressed in the compression chamber and then discharged out thereof into the discharge chamber 34 through its associated discharge port 43 while pushing open the discharge valve 43 a.

A supply passage 44 is formed in the cylinder block 11, the valve plate 14 and the rear housing 13 for connecting the discharge chamber 34 to the crank chamber 15. A bleed passage 45 is formed in the cylinder block 11, the valve plate 14 and the rear housing 13 for connecting the crank chamber 15 to the suction chamber 35. The bleed passage 45 has therein an orifice (not shown). As shown in FIG. 1, a displacement control valve 46 is disposed in the supply passage 44. For example, the displacement control valve 46 is similar in construction to that which is disclosed in Japanese Patent Application Publication No. 2003-239857. The supply passage 44, the bleed passage 45 and the displacement control valve 46 constitute the control mechanism 4 which is operable to control the pressure in the crank chamber 15.

The control mechanism 4 controls the opening and closing of the supply passage 44 by the displacement control valve 46 according to the variation of the pressure in the suction chamber 35 thereby to increase or decrease the pressure in the crank chamber 15 for regulating the displacement of the compressor 10. When cooling load is small and the pressure in the suction chamber 35 is low, the degree of opening of the displacement control valve 46 is increased thereby to increase the pressure in the crank chamber 15 and the inclination angle of the swash plate 25 is decreased, accordingly. As a result, the stroke of each piston 31 is decreased thereby to decrease the displacement of the compressor 10. On the other hand, when the cooling load is large and the pressure in the suction chamber 35 is high, the opening degree of the displacement control valve 46 is decreased thereby to decrease the pressure in the crank chamber 15 with the result that the inclination angle of the swash plate 25 is increased and the stroke of each of the pistons 31 is increased thereby to increase the displacement of the compressor 10. The opening degree of the displacement control valve 46 is variable externally according to the manner of operation such as acceleration of a vehicle or the like. The surface of the swash plate 25 facing toward the lug plate 24 provides a receiving surface 25 a as will be described later. The receiving surface 25 a comes into contact with the lug plate 24 thereby to regulate the maximum inclination angle of the swash plate 25.

The following will describe the construction of the hinge mechanism 26 in detail. In the compressor 10 of the preferred embodiment, the drive shaft 16 is rotated in the direction indicated by an arrow Z in FIG. 1. Referring to FIG. 4, reference symbol CP designates a first imaginary plane containing therein the top position A of the swash plate 25 and the longitudinal axial 01 of the drive shaft 16. The top position A of the swash plate 25 corresponds to the top dead center position of the piston 31, and more specifically places the piston 31 at its top dead center. The cross-section taken along this imaginary plane CP substantially corresponds to the cross-section of FIG. 1. Reference symbol SP in FIG. 4 designates a second imaginary plane which extends perpendicularly to the above plane CP. It is noted that the swash plate 25 is inclined at the maximum inclination angle in FIG. 1. In FIGS. 3 and 4, the left side and the right side of the swash plate 25 with respect to the first imaginary plane CP correspond to the side on which suction takes place and the other side on which discharge takes place in the compressor 10, respectively. In other words, in FIG. 1, the viewer side and the back side thereof correspond to the discharge side and the suction side, respectively. In FIG. 2, the viewer side and the back side thereof correspond to the suction side and the discharge side, respectively. Namely, FIG. 1 is a cross-sectional view of the compressor 10 showing the elements located on the suction side with respect to the first imaginary plane CP. FIG. 2 is an enlarged cross-sectional view of the compressor 10 showing the elements located on the discharge side with respect to the first imaginary plane CP.

The hinge mechanism 26 includes a support arm 61 and a guide pin 62 which are located on the suction side with respect to the first imaginary plane CP as shown in FIG. 1, and serve as a restraining hinge element 60. The hinge mechanism 26 also includes a first guide surface 71 and a second guide surface 72 which are located on the discharge side with respect to the first imaginary plane CP as shown in FIG. 2, and serve as a non-restraining hinge element 70. As shown in FIGS. 3 and 4, the guide pin 62 and the second guide surface 72 are provided on the front surface of the swash plate 25. As shown in FIGS. 1 and 2, the support arm 61 and the first guide surface 71 are provided on the rear surface of the lug plate 24 facing toward the swash plate 25 and correspondingly disposed in relation to the guide pin 62 and the second guide surface 72, respectively.

In the restraining hinge element 60, the support arm 61 has a guide hole 61 a with an inner circumferential surface, in which a spherical portion 62 a provided at the top end of the guide pin 62 is slidable. Thus, the support arm 61 and the guide pin 62 as the restraining hinge element 60 serve to restrain the lug plate 24 and the swash plate 25 from rotating relative to each other and the swash plate 25 from moving away from the lug plate 24.

In the non-restraining hinge element 70, the first and second guide surfaces 71 and 72 face each other and are contactable with each other. It is noted that the non-restraining hinge element 70 does not include a side wall for restraining the lug plate 24 and the swash plate 25 from rotating relative to each other and a side wall for restraining the swash plate 25 from moving away from the lug plate 24. Thus, the first and second guide surfaces 71 and 72 as the non-restraining hinge element 70 have no function of restraining the lug plate 24 and the swash plate 25 from rotating relative to each other and the swash plate 25 from moving away from the lug plate 24.

According to the above construction, when manufacturing the non-restraining hinge element 70, only the first and second guide surfaces 71 and 72, which support the swash plate 25 together with the restraining hinge element 60 so that the swash plate 25 is inclined at a desired angle, may be formed with high accuracy. Furthermore, the positioning accuracy of the first and second guide surfaces 71 and 72 relative to the restraining hinge element 60 may be lessened. Unlike the paired restraining hinges in the compressor disclosed in Japanese Patent Publication No. 2917767, therefore, there is no need to enlarge the clearance between the support arm 61 and the guide pin 62 of the restraining hinge element 60. Accordingly, it is possible to make the clearance between the support arm 61 and the guide pin 62 smaller by manufacturing these support arm 61 and guide pin 62 with the desired accuracy. More specifically, the clearance between the guide hole 61 a and the spherical portion 62 a can be easily made smaller by ensuring the accuracy of the directions of the axes of the guide hole 61 a and the guide pin 62 and of the diameters of the guide hole 61 a and the spherical portion 62 a. As a result, the swash plate 25 fits the restraining and non-restraining hinge elements 60 and 70 with less clearance (or backlash).

Thus, the restraining and non-restraining hinge elements 60 and 70 of the hinge mechanism 26 are provided between the swash plate 25 and the lug plate 24 and serve to support the swash plate 25 so that it is inclined at an angle as required. For example, when the swash plate 25 is inclined at the minimum inclination angle as shown in FIGS. 5 and 6, the hinge mechanism 26 supports the swash plate 25 with the guide pin 62 of the restraining hinge element 60 and the second guide surface 72 of the non-restraining hinge element 70 slid and located at certain positions.

The non-restraining hinge element 70 dispenses with a side wall for restraining the lug plate 24 and the swash plate 25 from rotating relative to each other, so that the non-restraining hinge 70 can be made light in weight.

The following will describe the receiving surface 25 a of the swash plate 25 in detail. Referring to FIGS. 1 through 4, the hinge mechanism 26 is located on the side of the top position A with respect to the second imaginary plane SP. The surface of the swash plate 25 facing toward the lug plate 24 provides the receiving surface 25 a which is located on the suction side with respect to the first imaginary plane CP and on the side of the bottom position B opposite to the top position A with respect to the second imaginary plane SP. The bottom position B corresponds to the bottom dead center position of the piston 31. The receiving surface 25 a is formed by smoothly machining a small area of a weight portion 25 b of the swash plate 25 projecting from the swash plate 25 toward the lug plate 24. The receiving surface 25 a is located at a position within a range where the receiving surface 25 a is contactable with the lug plate 24, which is furthest from the axis O1 of the drive shaft 16, that is, furthest from an intersecting point between a line O2 passing through the axes of the restraining hinge element 60 and the swash plate 25 and a line O3 passing through the center of the receiving surface 25 a and perpendicularly to the line O2, as shown in FIG. 4. In this way, the receiving surface 25 a is adapted to restrain the swash plate 25 from being inclined beyond the maximum inclination angle by contacting with the lug plate 24 when the swash plate 25 is inclined to its maximum inclination angle position as shown in FIG. 1.

The above-described compressor 10 of the preferred embodiment constitute together with the condenser 39, the expansion valve 40 and the evaporator 41 the refrigerant circuit 37, for example, for use in a vehicle. In the compressor 10, the drive shaft 16 is driven to rotate by the engine or the like as the external drive source thereby to rotate the swash plate 25 inclined at an angle through the restraining hinge element 60, which serves to restrain the lug plate 24 and the swash plate 25 from rotating relative to each other. The wobbling motion of the swash plate 25 is transmitted to the piston 31 through the shoes 32 thereby to reciprocate the piston 31 in the associated cylinder bore 11 a. Thus, the refrigerant gas is drawn from the suction chamber 35 into the compression chamber 33 in the cylinder bore 11 a, compressed and then discharged into the discharge chamber 34. The pressure in the crank chamber 15 is adjusted by the supply passage 44, the bleed passage 45 and the displacement control valve 46 to vary the inclination angle of the swash plate 25, thereby controlling the amount of the refrigerant gas discharged from the compression chamber 33 into the discharge chamber 34 (or the displacement of the compressor 10). Thus, cooling performance in accordance with the displacement of the compressor 10 is achieved by the refrigerant circuit 37.

During operation of the compressor 10, as shown in FIG. 7, a compression reactive force P1 and a suction force P2 of the refrigerant gas are applied to the swash plate 25 through the piston 31 and the shoes 32 thereby to create a moment M on the swash plate 25, which urges the swash plate to turn around the line of intersection between the swash plate 25 and the first imaginary plane CP to be inclined relative to the drive shaft 16. More specifically, the moment M acts on the swash plate 25 in such a way that the suction force P2 urges the swash plate 25 on the suction side of the first plane CP to move away from the lug plate 24 and the compression reactive force P1 urges the swash plate 25 on the discharge side of the first plane CP to press against the lug plate 24.

The support arm 61 and the guide pin 62 located on the suction side with respect to the first imaginary plane CP and serving as the restraining hinge element cooperate to restrain the swash plate 25 from moving away from the lug plate 24. Thus, the restraining hinge element 60 receives the part of the moment M that urges the swash plate 25 on the suction side with respect to the first imaginary plane CP to be moved away from the lug plate 24 by the suction force P2.

The first and second guide surfaces 71 and 72 as the non-restraining hinge element 70 receive the part of the moment M that urges the swash plate 25 on the discharge side with respect to the first imaginary plane CP to be pressed against the lug plate 24 by the compression reactive force P1. The part of the moment M that urges the swash plate 25 to be moved away from the lug plate 24 by the suction force P2 is not applied to the non-restraining hinge element 70, so that the non-restraining hinge element 70 does not need to restrain the swash plate 25 from moving away from the lug plate 24. When the compressor 10 is operating at a high speed and under a large displacement capacity in the state where the refrigerant gas is insufficient in the refrigerant circuit 37 and, therefore, the inertial force of the piston 31 becomes excessively large thereby to create a moment M that tends to further increase the inclination angle of the swash plate 25, the support arm 61 and the guide pin 62 as the restraining hinge element 60 of the hinge mechanism 26 can receive this moment M. Therefore, the compressor 10 does not generate noise and vibration which are caused by excessive inclination of the swash plate 25 beyond the maximum inclination angle. Namely, the compressor 10 reduces the generation of noise and vibration in operation.

In the compressor 10 of the preferred embodiment, the restraining hinge element 60 includes the support arm 61 which is provided on the lug plate 24 and has the guide hole 61 a with the inner circumferential surface, and the guide pin 62 which is provided on the swash plate 25 and has the spherical portion 62 a slidable in the guide hole 61 a. When the guide pin 62 slides in the guide hole 61 a, the spherical portion 62 a keeps a smooth contact with the inner circumferential surface of the guide hole 61 a, thus providing excellent durability for the hinge mechanism. The clearance between the guide hole 61 a and the spherical portion 62 a is easily made smaller by ensuring the accuracy of the directions of the axes of the guide hole 61 a and the guide pin 62 and of the diameters of the guide hole 61 a and the spherical portion 62 a. As a result, the above advantageous effect of reducing the generation of noise and vibration is achieved with more certainty.

In the compressor 10 of the preferred embodiment, the non-restraining hinge element 70 neither restrains nor need to restrain the lug plate 24 and the swash plate 25 from rotating relative to each other. Thus, weight reduction is achieved in addition to the above advantageous effect, thus improving the controllability of the compressor such as response to the variation of rotational speed of the drive shaft 16.

In the compressor 10 of the preferred embodiment, the non-restraining hinge element 70 includes the first guide surface 71 which is provided on the lug plate 24 and faces toward the swash plate 25 and the second guide surface 72 which is provided on the swash plate 25 and faces toward the first guide surface 71. When manufacturing the non-restraining hinge element 70, only the first and second guide surfaces 71 and 72 need to be machined with high accuracy and, therefore, the manufacturing of the non-restraining hinge element 70 is facilitated, with the result that production cost of the compressor 10 is further reduced.

In the compressor 10 of the preferred embodiment, the hinge mechanism 26 is located on the side of the top position A with respect to the second imaginary plane SP. This stabilizes the top dead center position of the piston 31 regardless of the inclination angle thereof. Thus, the volume of the compression chamber 33 that is defined by the head of the piston 31 located at the top dead center position (or top clearance) is made smaller, thereby suppressing the re-expansion of the refrigerant gas in the compression chamber 33.

Additionally, in the preferred embodiment, the swash plate 25 on the side of the top position A with respect to the second imaginary plane SP and on the suction side with respect to the first imaginary plane Cp is restrained from moving by the restraining hinge element 60. The swash plate 25 at the center thereof is restrained from moving by the parallel facing surfaces 23 of the elongated hole 22. However, the swash plate 25 is not restrained from turning about the line O2. When the compressor 10 operates at a low speed, the resultant force of the compression reactive force and the inertial force of the piston 31 is applied to the swash plate 25 on the discharge side with respect to the first imaginary plane CP and on the side of the top position A with respect to the second imaginary plane SP. Namely, the resultant force urges the portion of the swash plate 25 adjacent to the non-restraining hinge element 70 to press against the lug plate 24, that is, urges the second guide surface 72 to press against the first guide surface 71, thus stably supporting the swash plate 25.

When the compressor 10 operates at a high speed, for example, when the rotational speed of the drive shaft 16 is increased (e.g. 4000 to 5000 rpm or more), the resultant force is applied to the swash plate 25 on the side of the bottom position B opposite to the top position A with respect to the second imaginary plane SR Namely, the resultant force urges the portion of the swash plate 25 adjacent to the non-restraining hinge element 70 to move away from the lug plate 24, that is, urges the second guide surface 72 to move away from the first guide surface 71. However, the surface of the swash plate 25 facing toward the lug plate 24 provides the receiving surface 25 a which is located on the suction side with respect to the first imaginary plane CP and on the side of the bottom position B with respect to the second imaginary plane SP. When the rotational speed of the drive shaft 16 is increased (e.g. 4000 to 5000 rpm or more) and the swash plate 25 is inclined at the maximum inclination angle, the receiving surface 25 a is pressed against the lug plate 24. Thus, the portion of the swash plate 25 adjacent to the non-restraining hinge element 70, that is, the upper right portion of the swash plate 25 with respect to the line O2 shown in FIG. 4 is restrained from moving away from the lug plate 24.

It is preferable that the receiving surface 25 a should be smaller as long as it is located within the above contactable range. If the receiving surface 25 a is formed in a large area, the small area of the receiving surface 25 a may actually contact with the lug plate 24 due to the tolerance in assembling. In addition, large area of the receiving surface 25 a raises the production cost due to high accurate machining.

In the compressor 10 of the preferred embodiment, the receiving surface 25 a is easily formed on the weight portion 25 b of the swash plate 25. This contributes to the reduction in the production cost.

The receiving surface 25 a is located at the position in the range where it is contactable with the lug plate 24, which is furthest from the axis O1 of the drive shaft 16, thus appropriately receiving the force moving the swash plate 25 in the direction that causes the first and second guide surfaces 71 and 72 to move away from each other.

The compressor 10 of the preferred embodiment is adapted for use in a vehicle, and the drive shaft 16 is constantly driven while the engine of the vehicle is running. Thus, the compressor 10 often operates under a small displacement. Accordingly, the compressor 10 enhances the reduction in noise and vibration, which is one of the advantageous effects of the present invention.

In the compressor 10 of the preferred embodiment, the swash plate 25 includes the elongated hole 22 with the parallel facing surfaces 23 for receiving the outer circumferential surface of the drive shaft 16. This reduces the production cost as compared to the case where a sleeve is provided between the drive shaft 16 and the swash plate 25. The parallel facing surfaces 23 of the elongated hole 22 receive the part of the moment M that urges the swash plate 25 to turn around the line of intersection between the swash plate 25 and the first imaginary plane CP to be inclined relative to the drive shaft 16 by the compression reactive force P1 and the suction force P2. As described above, however, most of the moment M is received by the restraining hinge element 60 and the non-restraining hinge element 70. Thus, the parallel facing surfaces 23 of the elongated hole 22 keeps a smooth contact with the drive shaft 16, thereby suppressing the abrasion therebetween.

Alternatively, a sleeve may be provided between the swash plate 25 and the drive shaft 16. Like the hinge mechanism 26, the sleeve supports the swash plate 25 so that it is inclinable relative to the drive shaft 16 as disclosed in Japanese Patent Application publication No. 6-123281. The sleeve is also slidable relative to the outer circumferential surface of the drive shaft 16 in the axial direction of the drive shaft 16. The sleeve receives the part of the moment M that urges the swash plate 25 to turn around the line of intersection between the swash plate 25 and the first imaginary plane CP.

Alternatively, the support arm 61 may be provided on the swash plate 25, and the guide pin 62 may be provided on the lug plate 24. The first guide surface 71 may be provided on the swash plate 25, and the second guide surface 72 may be provided on the lug plate 24.

The present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims. 

1. A swash plate type variable displacement compressor for compressing a refrigerant, comprising: a housing defining therein a cylinder bore, a crank chamber, a suction chamber and a discharge chamber; a piston reciprocatably accommodated in the cylinder bore and defining a compression chamber in the cylinder bore; a drive shaft driven by an external drive source and rotatably supported by the housing; a lug plate supported by the drive shaft in the crank chamber so as to rotate with the drive shaft; a swash plate supported by the drive shaft in the crank chamber; a hinge mechanism provided between the lug plate and the swash plate, the swash plate being rotatable with and inclinable relative to the drive shaft through the lug plate and the hinge mechanism for reciprocating the piston through shoes; and a control mechanism operable to control a pressure in the crank chamber thereby to vary an amount of the refrigerant discharged from the compression chamber into the discharge chamber by the reciprocation of the piston based on an inclination angle of the swash plate, wherein the hinge mechanism includes a restraining hinge element that is located on a suction side with respect to a first imaginary plane that includes a top position of the swash plate corresponding to a top dead center position of the piston and an axis of the drive shaft for restraining the lug plate and the swash plate from rotating relative to each other and the swash plate to move away from the lug plate, the hinge mechanism further including a non-restraining hinge element that is located on a discharge side with respect to the first imaginary plane for not restraining the swash plate from moving away from the lug plate.
 2. The swash plate type variable displacement compressor according to claim 1, wherein the restraining hinge element includes a support arm that is provided on one of the lug plate and the swash plate and that has a guide hole with an inner circumferential surface and a guide pin that is provided on the other one of the lug plate and the swash plate and that has a spherical portion for sliding in the guide hole.
 3. The swash plate type variable displacement compressor according to claim 1, wherein the non-restraining hinge element is provided so as not to restrain the lug plate and the swash plate from rotating relative to each other.
 4. The swash plate type variable displacement compressor according to claim 3, wherein the non-restraining hinge element includes a first guide surface that is provided on one of the lug plate and the swash plate facing toward the other one of the lug plate and the swash plate and a second guide surface that is provided on the other one of the lug plate and the swash plate facing toward the first guide surface, the second guide surface being contactable with the first guide surface.
 5. The swash plate type variable displacement compressor according to claim 1, wherein the hinge mechanism is located on a side of the top position of the swash plate with respect to a second imaginary plane that includes the axis of the drive shaft and is perpendicular to the first imaginary plane, a surface of the swash plate that faces toward the lug plate providing a receiving surface that is located on the suction side with respect to the first imaginary plane and on a side opposite to the top position with respect to the second imaginary plane for contacting with the lug plate when the swash plate is inclined at a maximum inclination angle thereby to regulate the maximum inclination angle of the swash plate.
 6. The swash plate type variable displacement compressor according to claim 5, wherein the receiving surface is formed on a weight portion that is provided in the swash plate.
 7. The swash plate type variable displacement compressor according to claim 5, wherein the receiving surface is located at a position within a range where the receiving surface is contactable with the lug plate, which is furthest from the axis of the drive shaft.
 8. The swash plate type variable displacement compressor according to claim 1, wherein the drive shaft is constantly driven while the external drive source is running.
 9. The swash plate type variable displacement compressor according to claim 1, wherein the swash plate has an elongated hole with parallel facing surfaces for receiving an outer circumferential surface of the drive shaft.
 10. The swash plate type variable displacement compressor according to claim 1, wherein the control mechanism includes a supply passage for connecting the discharge chamber to the crank chamber, a bleed passage for connecting the crank chamber to the suction chamber and a displacement control valve disposed in the supply passage. 